Both State and Federal government have strict regulations governing hazardous organic and inorganic contaminants in the environment. Subsurface soil and groundwater contamination with organic and inorganic contaminants has been the concern of State and Federal government since the 1970's. Action levels and clean-up standards have been promulgated by both State and Federal government for numerous organic and inorganic contaminants. Regulated organic contaminants in the subsurface environment include, but are not limited to: polychlorinated biphenyls (PCBs); chlorinated volatile organic compounds (CVOCs) such as tetrachloroethene (PCE), trichloroethene (TCE), trichloroethane (TCA), dichloroethene (DCE), vinyl chloride; fuel constituents such as benzene, ethylbenzene, toluene, xylene, methyl tert butyl ether (MTBE), tertiary butyl alcohol (TBA), polynuclear aromatic hydrocarbons (PAHs), ethylene dibromide (EDB); pesticides such as (but not limited to) DDT; herbicides such as (but not limited to) silvex. Regulated inorganic contaminants in the subsurface environment include, but are not limited to: heavy metals, such as lead, arsenic, chromium, mercury, silver. The State and Federal regulations that govern these subsurface contaminants outline a protocol for subsurface investigation to identify the extent of contamination, identification of the human health and ecological risk posed by the contaminants, development of remedial action alternatives for reducing or eliminating any significant risk posed by the contaminants, and selection and implementation of remedial measures to achieve the remediation goals.
One method of subsurface investigation used to rapidly delineate the extent of hazardous organic and inorganic contaminants is known as direct push probe technology or direct push technology (DPT). Typically, this technology is used to assess organic contaminants in soil gas, soil, sediment, or groundwater. It is also used to assess inorganic contaminants in soil, sediment and groundwater.
DPT uses a vibratory percussion or slide hammer or pneumatics to advance a small diameter probe or push rod ranging from approximately 1 inch to 4-inch outside diameter into the soil and/or groundwater. DPT is typically mounted: 1) to a vehicle to be mobile, 2) to a support frame so that it can be moved inside a building for sub-slab investigation, or 3) to a boat or barge for evaluation of contaminants in sediment underlying a water body. DPT has been in existence since the late 1980's in the environmental investigation field as a means to rapidly collect soil, soil gas, and groundwater samples for contaminant analysis. DPT was much faster and cost effective as compared to conventional drilling methods using hollow stem augers or drive and wash casing advancement. Geoprobe Systems, Inc. and Simco Drilling Equipment, Inc. have emerged as leaders in the manufacture of DPT, among other competitors such as HydroPunch. Since the late 1980's most of the development effort in DPT has gone into geologic and contaminant investigative techniques to identify the soil type and contaminant(s) present in soil, soil gas, and groundwater. For example, there are probe techniques for collecting soil samples, soil gas samples, groundwater samples, identifying the soil lithology through electrical conductivity and cone penetrometer sensors. The American Society of Testing Materials (ASTM) has recently published a guidance document on the use of direct push technology for environmental investigations (D6724 Standard Guide for Selection and Installation of Direct Push Ground Water Monitoring Wells).